Gun propellant containing nonenergetic plasticizer,nitrocellulose and triaminoguanidine nitrate

ABSTRACT

NON-METALLIZED GUN PROPELLANT SYSTEMS ARE PROVIDED CONTAINING TRIAMINOGUANIDINE NITRATE OXIDIZER ALONE OR IN COMBINATION WITH OTHER OXIDIZERS SUCH AS CYCLOTRIMETHYLENE TRINITRAMINE OR CYCLOTETRAMETHYLENE TETRANITRAMINE. THE BINDER SYSTEM IS BASED ON NITROCELLULOSE AND A NONENERGETIC PLASTICIZER SUCH AS POLYETHYLENE GLYCOL.

United States Patent 3,732,130 GUN PROPELLANT CONTAINING NONENER- GETIC PLASTICIZER, NITROCELLULOSE AND TRIAMINOGUANIDINE NITRATE Joseph E. Flanagan, Woodland Hills, and Vernon E.

Haury, Santa Susana, Calif., assignors to North American Rockwell Corporation No Drawing. Filed Oct. 14, 1971, Ser. No. 192,717 Int. Cl. (306d 5/06 US. Cl. 149-18 Claims ABSTRACT OF THE DISCLOSURE Non-metallized gun propellant systems are provided containing triaminoguanidine nitrate oxidizer alone or in combination with other oxidizers such as cyclotrimethylene trinitramine or cyclotetramethylene tetranitramine. The binder system is based on nitrocellulose and a nonenergetic plasticizer such as polyethylene glycol.

CROSS-REFERENCE TO RELATED APPLICATION This application is related to application Ser. No. 192,718 filed concurrently herewith by V. E. Haury, a co-inventor herein, and M. B. Frankel for Gun Propellant Containing Nitroplasticized Nitrocellulose and Triaminoguanidine Nitrate.

BACKGROUND OF THE INVENTION This invention relates to gun propellants which are generically defined herein as propellants for propelling projectiles. Specifically, this invention is concerned with gun propellants containing plasticized nitrocellulose binder in which the plasticizer is non-energetic and triaminoguanidine nitrate oxidizer alone or in combination with other oxidizers such as cyclotrimethylene trinitramine or cyclotetramethylene tetranitramine.

Gun propellants are referred to as low explosives to distinguish them from detonating high explosives and differ from high explosives in that the rate of energy release by autocombustion is controlled within certain limitations. The first real gun propellant was made from potassium nitrate, sulfur and charcoal and was referred to as black powder. Nitrocellulose forms the basis for all modern gunpowders and is typically combined today with nitroglycerine to form a smokeless powder. Smokeless powder refers to colloided nitrocellulose either alone or in admixture with nitroglycerine or other materials. Smokeless powders are not in reality powders in the common sense of the word, nor are they smokeless, except when compared with black powder. Modern powders may take many forms including flakes, strips, pellets and cylinders. However, the cylindrical grain is most commonly employed for military purposes. Single-base powders generally refer to colloided nitrocellulose in the absence of nitroglycerine or other plasticizer. The terminology double-base powder generally refers to powders containing nitrocellulose and nitroglycerine or other plasticizer. These double-base powders usually contain from to 40% nitroglycerin. Although double-base powders have many desirable characteristics, they also have many undesirable performance features including a high burning temperature which causes excessive barrel erosion when compared with single-base powders. Additionally, nitroglycerine is hazardous to handle.

Since the beginning of the twentieth century, the fundamental nature of solid propellant compositions used in small arms ammunition and the like has remained substantially unchanged. While improvements have been made, such as the introduction of ball propellant, cool burning extruded compositions, and the utilization of deterrents and geometries to improve control of gas evolution, the formulations are still based primarily upon ntijtrocellulose with or without nitroglycerine as indicated a ove.

The early single-base gun propellant, utilizing nitrocellulose with 13.15% nitrogen content, has a mass impetus of 357,000 ft.-lbs./lb. and an isochoric flame temperature of 3292 K. Incorporation of 20 weight percent of nitroglycerin gives the standard double-base propellant with a mass impetus of 378,000 ft.-lbs./lb. and an isochoric flame temperature of 3592 K. As mentioned previously, the high flame temperature of the doublebase system is very undesirable since it severely limits the barrel life of the gun due to barrel erosion. To overcome this critical problem, triple-base gun propellants were developed in which nitroguanidine was incorporated as a coolant into the nitrocellulose-nitroglycerine system. Representative conventional triple base propellants are the M30 (impetus=364,000 ft.-lbs./lb.; T =3040 K.) and the M31 (impetus=335,000 ft.lbs./lb.; T =2597 K.)

The concurrently filed application of Haury et al., supra, discloses non-metallized gun propellants containing plasticized nitrocellulose binder and triaminoguanidine nitrate oxidizer alone or in combination with other oxidizers such as cyclotrimethylene trinitramine or cyclotetramethylene tetranitrarnine. The plasticized nitrocellulose binder is typically a highly nitroplasticized nitrocellulose binder and the plasticizer is preferably a blend of trimethylolethane trinitrate and triethylene glycol dinitrate. These highly nitroplasticized nitrocellulose-based gun propellants have a mass impetus which is generally above that of the standard double-base system and an isochoric flame temperature which is typically below 3000 K.

SUMMARY OF THE INVENTION It has now been discovered that improved triaminoguanidine nitrate containing nitrocellulose-based gun propellants can be formulated using non-energetic plasticizers such as polyethylene glycol. Secondary oxidizers such as cyclotrimethylene trinitramine and cyclotetramethylene tetranitramine can be added to the propellant composition if desired. The present gun propellant systems are highly flexible and permit the formulation of propellants with a wide range of mass impetus characteristics and low flame temperatures, usually well below 3000 K. when measured at constant volume.

In accordance with the foregoing, it is an object of this invention to provide improved solid propellants and particularly improved solid propellants for propelling projectiles.

A further object of the invention is to provide gun propellants with low flame temperatures in order to avoid excessive gun barrel erosion.

A still further object of the invention is to provide gun propellant compositions which can be formulated with a wide range of mass impetus.

An additional object of the invention is to provide gun propellant compositions which evolve non-corrosive combustion products when burned and yet are capable of manufacture by standard equipment into non-, monoor multi-perforated gun-type grains.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present gun propellants do not contain metal fuels since metal particles in the propellant exhaust lead to undesirable gun barrel erosion. The gun propellants preferably contain only carbon-hydrogen-oxygen-nitrogen in order to obtain an all gaseous, non-corrosive combustion product. The components of the gun propellant compositions are preferably high nitrogen and hydrogen containing materials which have low carbon and oxygen content in order to avoid high average molecular weight exhaust products since a low molecular weight of the combustion products is desirable to increase the value of the specific impulse.

Triaminoguanidine nitrate (TAGN) is a dense, nonhygroscopie, thermally stable solid and is readily prepared used, that the molecular Weight of this component not exceed about 4000. The plasticizer will usually be present in about to 20 weight percent of the gun propellant composition.

Conventional stabilizers are added to the gun propellants in high yields from guanidine nitrate and hydrazine (Dia- 5 to insure acceptable stability, or in other words, acceptmond, L. H., Derivatives of Hydrazine, Publication No. able resistance to chemical deterioration. Illustrative sta- 10, 466, University Microfilms, Ann Arbor, Mich., 1954). bilizers include nitrodiphenylamine (NDPA) and ethyl It can also be prepared by the aqueous fusion of calcium centralite (EC) (N,N'-diethylcarbonilide). The quantity cyanamide and hydrazine nitrate and also by reacting a of stabilizer added to the propellant 1s typ1cally /2 to 1 /2 f??? 3"? 9 8Z Gii i i ii' a f th' tb famed dic an iami e at. unc 10118 e prope an 0 1s mven lOIl may e manu as an oxidizer and coolant in the propellent system and utilizing conventional smokeless powder equipment. The has been found to allow the attainment of higher mass individual grains are of conventional size and may be nonimpetus and lower flame temperatures than can be obperforated, mono-perforated or multi-perforated, such as tained by the use of conventional coolants such as nitrograin; corlltaining seven perfcrations. The grams may be uanidine and oxamide. TAGN is used alone or in concy in rica or rosette in con guratlon. j unction with other oxidizers such as cyclotrimethylene Table I lists the composition of eight preferred gun trinitramine and cyclotetramethylene tetranitramine. Varipropellants falling within the scope of the present inven- 3$135 5???531 5333133155? a fid iifi iiile iiiifi E31;122 .$1313ilifiiiiaiiiifif firfit103 3222553;

s nil: and physical properties of the propellant grain desystems are highly flexible and permit the formulation sired. Conventional stabilizers are added to the binder 3f propellants with a Iii/id; ratngel 1of imlpetils anid low system as will be discussed below. ame temperatures. 11 ac a o e 1 us rate gun The TAGN will normally comprise from 40 to 80 propellant formulations have theoretical 1sochor1c flame weight percent of the propellant compositlon. It is gentemperatures well below 3000 K.

TABLE I Weight percent Gun propellant formulation number 1 2 3 4 5 6 7 8 $iEN 60.0 54.0 40.0 70.0 76.0 05.0 70.0 60.0 HMX 14.0 20.0 23.0 BinderiNt'JPqgzbMNev 20.0 17.5 15.0 24.0 10.0 29.0 19.0 19.0 fririiffff'. -l 5.0 7.5 10.0 5.0 7.0 5.0 10.0 15.0 Stabilizer: N PDa 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0

e a 1%d. B i 374.2 372.3 372.3 350.7 351.1 355.1 337.8 315.0 T.,K. (53100.) 2,023 2, 587 2,580 2,439 2,325 2,459 2,219 2, 040

erally preferred that the solid propellant composition con- 40 The following example demonstrates the preparation tain about 50 to 70 weight percent TAGN with the reof a preferred composition of the present invention: mainder of the composition comprising plasticized nltro- EXAMPLE cellulose binder. As previously stated, the TAGN oxldlzer Ingredient: Weight percent can either be used alone or in combination with other TAGN 755 oxidizers. It is generally preferred to reduce the amount HMX 7.5 of TAGN employed by the amount of secondary oxidizer NC (126% N) 130 added. Cyclotrimethylene trinitramine (RDX) and cyclo- PEG (M.W 400) 4'0 tetramethylene tetranitramine (HMX) are the preferred NDPA 05 secondary oxidizers since they have relatively high nitrogen and hydrogen contents and relatively low carbon and T mgreqlents were thoroughly mlXed In a 0 oxygen contents, relatively high pos1t1ve heats of formahOflZOIltal mixer at ambient temperature to form a 50 tion, high density, satisfactory thermostability and reasonable impact sensitivity as well as being nonhygroscopic. The gun propellants ordinarily will contain from about 0 to 30 weight percent RDX or HMX, and preferably about 15 to 25 weight percent.

The gun propellant binder is plasticized nitrocellulose. The nitrocellulose (NC) content of the composition will normally vary in the range of 10 to 30% by weight and will preferably be in the range of 15 to 25% by weight. The weight percent of nitrogen in the nitrocellulose will normally be in the range of 12.5 to 13.5% as is conventional in smokeless powder formulations.

The exact non-energetic plasticizer employed for the nitrocellulose binder will depend upon the mass impetus of the gun propellant composition which is required, the flame temperature desired and the physical properties of the final propellant grain which must be attained. The preferred non-energetic plasticizers are the polyalkylene glycols such as polyethylene glycol (PEG) and polypropylene glycol and their alkyl ether derivatives such as butyl carbitol (diethylene glycol butylether). It is preferred that the plasticizer be liquid so that the propellant can be easily formulated. For example, it is generally preferred that the molecular weight of the polyethylene glycol not exceed about 600 and, if polypropylene glycol is gram batch of propellant and then pressed into strips. The strips were cured at 30 C. for 48 hours. Impact sensitivity, thermal stability (Taliani) and autoignition characteristics of the propellant were measured. These physical properties as well as some thermodynamic properties of the propellant are summarized in Table II.

volume (2.0 cubic inch) impetus bomb. Thin strips of propellant formulation No. 5 in Table I (0.03 inch) were cut into small discs (0.3 inch diameter) and placed in the impetus bomb. Hot-Wire ignition was utilized so that no correction was necessary for the igniter. The maximum pressure rise of the ignited propellant was 92% that of the theoretical pressure rise. By comparison, standard M-IO propellant [by weight about 97% nitrocellulose (13.15% N), 1% diphenylamine, 0.1% graphite, 1.5% ethyl alcohol and 0.5% water] will yield only about 85% of the expected pressure rise.

As further illustrative of the present invention, propellant formulation No. 7 in Table I was formed into a 7- perforated grain containing 12 grams and was fired in a 20 mm. Mann. barrel. The length of the propellant grain was 0.17 in., the diameter was 0.19 in. and the perforations were 0.026 in. A maximum pressure of 23 k.p.s.i. was obtained in this firing. These tests demonstrated that, although the weight and size of the propellant charge were not optimized, smooth ignition and combustion were obtained.

It will be obvious to those skilled in the art that other non-energetic plasticizers as well as other stabilizers and secondary oxidizers can be substituted for the illustrated ingredients. For example, the secondary oxidizer could be methylene or ethylene dinitramine rather than RDX or HMX.

The above description is for the purpose of illustration and clarification only and it is intended that the scope of the invention not be limited except by reference to the appended claims.

We claim:

1. A non-metallized solid gun propellant composition comprising a cured intimate mixture of triaminoguanidine nitrate, non-energetic plasticizer and nitrocellulose.

2. The solid gun propellant composition of claim 1 in which the composition contains, by weight, 40 to 80% of triaminognanidine nitrate.

3. The solid gun propellant composition of claim 1 in which the composition contains, by weight, 50 to 70% of triaminoguanidine nitrate.

4. A non-metallized solid gun propellant composition comprising a cured intimate mixture of, by weight, to triaminoguanidine nitrate, 0 to 30% of cyclotrimethylene trinitramine or cyclotetramethylene tetranitramine, 10 to 30% of nitrocellulose and from 5 to 20% of a non-energetic plasticizer for said nitrocellulose.

5. The solid gun propellant composition of claim 4 in which the plasticizer is a polyalkylene glycol.

6. The solid gun propellant composition of claim 5 in which the polyalkylene glycol is polyethylene glycol or polypropylene glycol.

7. The solid gun propellant composition of claim 5 in which the polyalkylene glycol is an alkyl ether substituted polyalkylene glycol.

8. The solid gun propellant composition of claim 7 in which the alkyl ether substituted polyalkylene glycol is butyl carbitol.

9. .The solid gun propellant composition of claim 4 in which the composition is in the form of a multi-perforated grain.

10. The solid gun propellant composition of claim 9 in which the grain has seven perforations.

References Cited UNITED STATES PATENTS 2,929,699 3/1960 Audrieth et al. 14992 X 3,110,258 11/1963 Weber 149-92 X 3,338,762 8/1967 Oja 14936 X 3,400,025 9/1968 Hopper et al. 14918 3,447,983 6/1969 Camp et a1 14918 3,506,505 4/1970 Herzog et al 149-100 X 3,639,183 2/1972 Crescenzo et al 14992 X CARL D. QUARFORTH, Primary Examiner E. A. MILLER, Assistant Examiner US. Cl. X.R. 149-36, 92, 

